In commonly assigned U.S. Pat. Nos. 4,933,780 and 5,016,030, a photographic filmstrip having a virtually transparent, magnetic film layer on the non-emulsion side of the filmstrip (referred to as an MOF layer) is disclosed in conjunction with various camera systems. One or more longitudinal read/write tracks are illustrated in the MOF layer between the side edges of the image frame area and the filmstrip where information such as film type, film speed, film exposure information, and information relevant to the processing and subsequent use, e.g., printing, of the exposed image frames is pre-recorded during manufacture of the filmstrip cartridge. The cameras disclosed therein provide for reading out the pre-recorded information useful for controlling camera operations and recording of information on certain other tracks during camera use. The information recorded during camera use may include voiced messages or sound associated with the photographed scene and may be recorded in digital or analog format on the certain tracks. It is contemplated that both the pre-recorded and the camera use recorded information will be read out for control and reprint purposes during photofinishing. Also, it is desirable for the photofinisher to have the capability to record additional information related to finishing, e.g., printing exposure conditions, customer information, reorder information, etc., in further tracks.
A photographic filmstrip is described in detail in commonly assigned U.S. Pat. No. 5,229,810, for example, incorporated herein by reference, having an optically transparent MOF layer continuously coated on the non-emulsion side of the filmstrip base. Turning first to FIGS. 1A and 1B, they schematically depict such a filmstrip 100 of the type described in the '810 patent having a base 110 with photographic emulsion layers 115 on one side and a virtually transparent MOF layer 120 on the non-emulsion side. An anti-static and lubricating layer 122 covers the MOF layer 120, and perforations 125 are provided for metering image frame areas through a camera exposure gate. Each image frame area of the filmstrip 100 includes a set of edge strip regions of the MOF layer 120, e.g., regions 100a and 100b, including record/reproduce track pairs C0, C1 and C2, C3 adjacent to respective filmstrip edges 102 and 104. A central image frame region of the MOF layer 120 includes tracks F00-F29 extending the image frame length 100a. The filmstrip 100 has a predetermined nominal width 108 for the filmstrip type, and tracks C0-C3 and F00-F29 have defined widths.
As described in the '810 patent in detail, the edge tracks C0-C3 are intended to be used for recording exposure related information in a camera having edge mounted magnetic recording heads. Certain of the tracks F00-F29 are intended to contain filmstrip type information pre-recorded by the filmstrip manufacturer, and other of the tracks F00-F29 are reserved for recording information during photofinishing.
In a variation of the filmstrip 100, recording and reproducing in the tracks F00-F29 is not practiced, and the MOF layer 120 may or may not be coated over the image frame area. In this variation, one or more of the tracks C0-C3 in the edge regions 100a and 100b are used for recording print related information, e.g., the color correction and exposure data applied in the most recent set of prints made from the image frames. In such photofinishing equipment as described in the above-referenced U.S. Ser. No. 08/171,582 application, certain of the tracks are read out prior to printing to control printing operations, and the print related information is recorded in the recording tracks contemporaneously with making the print exposure.
The photographic filmstrip 100 is of much greater thickness than the magnetic tape used for commercial and consumer recording and reproduction and is neither compliant nor inherently flat. When removed from its cartridge, such a filmstrip shows a relatively high stiffness and very observable cross-curvature across its width that is convex on or toward the emulsion side of the filmstrip. Further, the unwrapped filmstrip also shows a convex curvature along its length, again on the non-emulsion side of the film. This latter curvature is attributed primarily to a core-set curl that results from the filmstrip having been tightly wound on a film cartridge spool.
The cross-film curvature or curl across the width of the filmstrip is primarily caused by the number of multilayers of emulsion and MOF layer. The emulsion and MOF multilayers have different stretch properties than that of the base film substrate of acetate, PET, or PEN material. The cross-film curl is also influenced by the bending phenomena known as anticlastic curvature. The degree of cross-film curl also depends on environmental conditions, including the time and temperature history of the film, the relative humidity, and the thickness of the film.
Because of the cross-film curl, it is difficult to achieve good contact or compliance across the width of a magnetic read/write head. To provide a reliable read or write signal, the length of the magnetic recording head gap must remain in close proximity to the magnetic coating. Any disturbances, such as variations in cross film curl, can vary the relationship of the recording head gap to the magnetic coating and decrease the reliability of the signal.
Therefore, it is necessary to the extent possible to flatten out the transverse or cross film curl particularly at the side edge regions 100a, 100b where the MOF recording tracks C0-C3 are situated, to provide the flat plane during read out of tracks C0-C3 and to track the filmstrip edges 102, 104 as closely as possible.
Commonly assigned U.S. Pat. Nos. 5,034,836, 5,041,933, 5,274,522, 5,285,324 and 5,285,325 and further U.S. Pat. No. 5,307,100 disclose magnetic recording head configurations for use in recording and/or reproducing in longitudinal tracks alongside the filmstrip edges, but not in the image frame area. These patents showing magnetic recording heads for recording along the edges of the filmstrip outside the image area generally teach shaping the magnetic record/reproduce heads as arc sections of a cylinder and either flattening the filmstrip or wrapping or conforming the filmstrip MOF layer over the arc section to provide a line contact of the magnetic head gap with the MOF layer. Pressure pad supports or rollers on the emulsion side opposite from the recording heads and continuous motion of the filmstrip are taught to provide compliance for recording and/or reproducing information.
These arrangements cause the filmstrip to be wrapped or straightened against its inherent cross-film and longitudinal curl. This can cause the edge strip regions 100a and 100b to be inclined to curl away from the magnetic head gaps in the head gap length direction extending toward the side edges 102,104.
In a photographic filmstrip bearing a MOF layer as described above, the density of the virtually transparent MOF layer is much lower than in magnetic tape. Because of the low magnetic density of the MOF layer and the susceptibility of the emulsion side to scratching and damage, it is of particular importance that the magnetic read/write head-to-film interface must have high compliance.
Problems to be Solved by the Invention
The invention is directed to solving the above stated problems of recording and reproducing information on MOF layers of a filmstrip, particularly in filmstrip processing, handling or other apparatus, while avoiding damage to the filmstrip.